These maps are open-filed as they become available, initially as PDF
files of scans of the hand-drawn linework and later as full color maps
and GIS products. Following cartographic production and editorial review,
these maps may be published within our GM-series or
be included in larger maps of regions of particular interest.

These maps are subject to frequent revisions and may be unavailable
when being revised. Map Reference dates show the time of initial
compilation; Map Revision dates, when given, indicate the
most current version of the map; Last Modified dates for files may not, accurately reflect the time the map was last revised.